Stanford psychologist Carol Dweck has spent three decades trying to figure out why some people flourish in business while others of equal talent don’t. Her conclusion, presented in her 2006 book Mindset: The New Psychology of Success, is that people who think that their intelligence and talents can grow over time are successful while people who think they are stuck with what they’re born with don’t.

“People who believe in the power of talent tend not to fulfill their potential because they’re so concerned with looking smart and not making mistakes. But people who believe that talent can be developed are the ones who really push, stretch, confront their own mistakes and learn from them,” says Dweck.

Here’s one reason why this it is so important for a leader to believe in his or her own growth potential. As businesses grow, they require different things from their leaders. The talents and skills that bring success at one stage of a firm’s development are not the same as those required at another stage.

In Navigating the Growth Curve, James Fischer describes seven stages of growth, from start-up to about 350 employees, and identifies key reasons why many companies get stuck at one stage or another. One of the most common reasons companies get stuck is that leaders are unable to change how they show up at work.

The leadership skills, attitudes, and approaches that are required to get a company off the ground are very different from those required once the enterprise grows much beyond 20 employees. That’s one reason so many companies get to about 20 employees and stagnate. After all, of the 27 million small businesses in the US, only 600,000, or 2.2%, have more than 20 employees.

Do you have a growth mind-set? If you don’t, you’d better develop one. Otherwise you’re likely to get stuck.